FT-ICR-MS analysis of lignin

Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) of a steam-exploded lignin from wheat straw showed that fragments with a mass higher than 4534?Da cannot be obtained. Furthermore, FT-ICR-MS showed that lignin is not a completely random polymer, but shows some regularity with a difference of 44.026?m/z (C?H?O) between the peaks. The distribution of Kendrick mass defect in the function of Kendrick nominal masses showed the same behaviour. FT-ICR-MS analysis of bagasse lignin (Granit) showed that the largest value of mass found was 4347?Da. The peaks show regularities with a difference of 44.026?m/z between the peaks. The organosolv lignin showed that the polymer with the largest mass value was 3699?Da in FT-ICR-MS. The analysis of the peaks did not show regularity; however, the Kendrick diagram for this lignin showed the same slope as in the other samples, in agreement with the C?H?O regular difference between peaks.     

Hyperbranched Polylysine: A Versatile,Biodegradable Transfection Agent for the Production of Recombinant Proteins by Transient Gene Expression and the Transfection of Primary Cells

The feasibility of a new transfection agent, HBPL, for the production of recombinant IgG antibody via TGE as well as for the transfection of primary cells is studied. Under the conditions investigated, transfection of CHO‐DG44 cells using HBPL results in IgG yields that are comparable to those obtained with PEI. In experiments with CHO‐K1 cells and MEFs the use of HPBL allows to achieve transfection efficiencies comparable to or better than those obtained with PEI or Fugene®. HBPL‐mediated transfection does not require complex pre‐formation, works well in serum‐containing media and is biodegradable, which may prevent cumulative cytotoxicity and facilitates downstream processing.

     

The toxicity outcome of silica nanoparticles (Ludox?) is influenced by testing techniques and treatment modalities

We analyzed the influence of the kind of cytotoxicity test and its application modality in defining the level of hazard of the in vitro exposures to nanostructures. We assessed the cytotoxicity induced by two different Ludox? silica nanoparticles (NPs), AS30 and SM30, on three human cell lines, CCD-34Lu, A549, and HT-1080. Dynamic light scattering measurements showed particle agglomeration when NPs are diluted in culture medium supplemented with fetal calf serum. We examined the impact of such particle aggregation on the cytotoxicity by exposing the cells to NPs under different treatment modalities: short incubation (2?h) in serum-free medium or long incubation (24–72?h) in serum-containing medium. Under this last modality, NP suspensions tended to form aggregates and were toxic at concentrations five- to tenfold higher than in serum-free medium. The results of cell survival varied considerably when the long-term clonogenic assay was performed to validate the data of the short-term MTS assay. Indeed, the half maximum effective concentrations (EC₅₀) in all the three cell lines were four- to fivefold lower when calculated from the data of clonogenic assay than of MTS. Moreover, the mechanisms of NP toxicity were cell-type-specific, showing that CCD-34Lu are prone to the induction of plasma membrane damages and HT-1080 are prone to DNA double-strand break and apoptosis induction. Taken together, our results demonstrate that the choice of testing strategy and treatment conditions plays an important role in assessing the in vitro toxicity of NPs.

NIR emission of cyclic [4]rotaxanes containing π-extended porphyrin chromophores

The photophysical properties of a Cu(I) [4]rotaxane 4(4+) and of the demetalated [4]rotaxane 3 have been determined and compared to those of the component Zn porphyrin 2. All samples emit in the NIR region (700-1200 nm). The luminescence from the interlocked structures is bathochromically shifted with respect to 2 and displays a lower emission quantum yield, much lower for 4(4+) than for 3. The occurrence of intra-molecular electron or energy transfer is excluded and the decrease in luminescence yield is discussed in terms of the energy gap law and of electronic interactions between components of the cyclic interlocked structure. In toluene a dual emission behavior, similar to that of 2, is observed for 3 and ascribed to the presence of two non-equilibrated excited states, π-π* and CT in nature with lifetimes of 0.80 and 0.14 ns, respectively.     

Spectroscopic understanding of ultra-high rate performance for LiMn(0.75)Fe(0.25)PO4 nanorods-graphene hybrid in lithium ion battery

Comprehensive X-ray absorption near-edge structure spectroscopy at the C, O and Li K-edges and the Mn, Fe, and P L-edges of LiMn(0.75)Fe(0.25)PO(4) nanorods-graphene has been reported in great detail. Compared to that of free standing graphene and LiMn(0.75)Fe(0.25)PO(4), the intimate interaction between the nanorods and graphene via charge redistribution has been unambiguously confirmed. This interaction not only anchors the nanorods onto the graphene but also modifies its surface chemistry, both of which afford the nanorods-graphene hybrid an ultra-high rate performance in lithium ion batteries. Such knowledge is important for the understanding of hybrid nanomaterials for lithium ion batteries and allows rational design for further improvements in performance.     

X‐ray and DFT studies of a mono‐ and binuclear copper(II) ionic compound containing a Schiff base

In the structure of trans‐bis(ethanol‐κO)tetrakis(1H‐imidazole‐κN³)copper(II) bis[μ‐N‐(2‐oxidobenzylidene)‐D,L‐glutamato]‐κ⁴O¹,N,O^2′:O^2′;κ⁴O^2′:O¹,N,O^2′‐bis[(1H‐imidazole‐κN³)cuprate(II)], [Cu(C₃H₄N₂)₄(C₂H₆O)₂][Cu₂(C₁₅H₁₄N₃O₅)₂], both ions are located on centres of inversion. The cation is mononuclear, showing a distorted octahedral coordination, while the anion is a binuclear centrosymmetric dimer with a square‐pyramidal copper(II) coordination. An extensive three‐dimensional hydrogen‐bonding network is formed between the ions. According to B3LYP/6–31G* calculations, the two equivalent components of the anion are in doublet states (spin density located mostly on Cu^II ions) and are coupled as a triplet, with only marginal preference over an open‐shell singlet.     

Stereoselectivity in metallocene-catalyzed coordination polymerization of renewable methylene butyrolactones: from stereo-random to stereo-perfect polymers

Coordination polymerization of renewable α-methylene-γ-(methyl)butyrolactones by chiral C(2)-symmetric zirconocene catalysts produces stereo-random, highly stereo-regular, or perfectly stereo-regular polymers, depending on the monomer and catalyst structures. Computational studies yield a fundamental understanding of the stereocontrol mechanism governing these new polymerization reactions mediated by chiral metallocenium catalysts.     

On Maximally Inflected Hyperbolic Curves

In this note we study the distribution of real inflection points among the ovals of a real non-singular hyperbolic curve of even degree. Using Hilbert’s method we show that for any integers \(d\) and \(r\) such that \(4\le r \le 2d^2-2d\) , there is a non-singular hyperbolic curve of degree \(2d\) in \({\mathbb R}^2\) with exactly \(r\) line segments in the boundary of its convex hull. We also give a complete classification of possible distributions of inflection points among the ovals of a maximally inflected non-singular hyperbolic curve of degree \(6\) .     

Difference Galois theory of linear differential equations

We develop a Galois theory for linear differential equations equipped with the action of an endomorphism. This theory is aimed at studying the difference algebraic relations among the solutions of a linear differential equation. The Galois groups here are linear difference algebraic groups, i.e., matrix groups defined by algebraic difference equations.     

A constructive algebraic strategy for interpolatory subdivision schemes induced by bivariate box splines

This paper describes an algebraic construction of bivariate interpolatory subdivision masks induced by three-directional box spline subdivision schemes. Specifically, given a three-directional box spline, we address the problem of defining a corresponding interpolatory subdivision scheme by constructing an appropriate correction mask to convolve with the three-directional box spline mask. The proposed approach is based on the analysis of certain polynomial identities in two variables and leads to interesting new interpolatory bivariate subdivision schemes.